CHT sensors vs thermostat housing

J

jberbrich

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My fan still comes on full speed after 5 miles of driving, even when it is 60 degrees and raining. I saw a post by someone that had a mangled thermostat housing that was causing similar problems. I know for a fact that my thermostast housing is mangled inside. I replaced the thermostast a few months ago to try to resolve fan issue, and noticed that the inside looks like someone chopped away at it with a knife. There is no smoothe, flat surface for the new thermostat to rest against the lip on the housing. Would this cause a slightly warm running engine that would kick the fan on full speed?

Also, how difficult is it to change the cylinder head temperature sensors, as I have read that this may also be the culprit(s)?

I'm going to keep replacing cooling system stuff until I "ger-r-done".

Thanks guys.
 
I wouldn't think that coolant leaking past the thermostat would cause over-heating - more the opposite.

The CHT is under the intake manifold, just inside cylinder #4, so you have to pull the intake off.
 
If the fan doesn't kick into high until the engine has run for a few minutes, it's not going to be the temperature sensors or wiring.

If this is a gen II car, I'd replace the thermostat housing (front) and the coolant outlet pipe (rear) at the least. You should also replace the degas tank if you haven't already. I suspect that you have a leak and the cooling system is not pressurizing and may have trapped air in it. You can verify this by having a pressure leak-down test done.
 
On my 2004 LSV8, the thermostat is weird and is twist locked onto 2 plastic ears inside the thermostat housing. If one or both breaks off, the thermostat may get stuck and you could overheat.

My Tstat housing plastic ear broke off at about 100K miles, no outside visible symptoms other than an occsional high temp reading at unexpected times. You can see the tstat crooked in the housing if you look thru the fill cap over the front of the engine. It won't be obvious unless you already know to look for it.

The plastic ears are about 1/2 inch cubes on either side of the opening. Unlike all the other cars I have ever owned, the LS T stat does not just sit on a flat surface. It requires twist locking under spring pressure against those ears.

Jim Henderson
 
Thermostast Housing Ears?

Jim Henderson said:
On my 2004 LSV8, the thermostat is weird and is twist locked onto 2 plastic ears inside the thermostat housing. If one or both breaks off, the thermostat may get stuck and you could overheat.

My Tstat housing plastic ear broke off at about 100K miles, no outside visible symptoms other than an occsional high temp reading at unexpected times. You can see the tstat crooked in the housing if you look thru the fill cap over the front of the engine. It won't be obvious unless you already know to look for it.

The plastic ears are about 1/2 inch cubes on either side of the opening. Unlike all the other cars I have ever owned, the LS T stat does not just sit on a flat surface. It requires twist locking under spring pressure against those ears.

Jim Henderson
Click to expand...

Thaks for the good info Jim. It may be that those plastic ears have broken off and left a jagged edge inside the thermostat housing. Now I know why people are replacing their thermostat housings. Are there metal or aluminum ones available?

I don't know why broken housing ears would kick my fan on high though, even when the outside air is cool and I am doing 70 on the freeway. The radiator is clear. I know that I don't have air in the system because I had it bled twice by the dealer. He said the second bleed produced no air. Any more ideas?
 
Thanks

joegr said:
If the fan doesn't kick into high until the engine has run for a few minutes, it's not going to be the temperature sensors or wiring.

If this is a gen II car, I'd replace the thermostat housing (front) and the coolant outlet pipe (rear) at the least. You should also replace the degas tank if you haven't already. I suspect that you have a leak and the cooling system is not pressurizing and may have trapped air in it. You can verify this by having a pressure leak-down test done.
Click to expand...


Thanks. I have had the car bled twice by the dealer, with no air on the second bleed. Are you suggesting that I replace the T-stat housing because fo the broken ears mentioned by Jim Henerson? If I replace the housing and coolant outlet pipe, I presume I will have to have the system bled again and again, again right? SONOFA...
 
is the inside temperature gauge also indicating over-heating, or at least - at temp - when the fan kicks on ?
 
jberbrich said:
Thanks. I have had the car bled twice by the dealer, with no air on the second bleed. Are you suggesting that I replace the T-stat housing because fo the broken ears mentioned by Jim Henerson? If I replace the housing and coolant outlet pipe, I presume I will have to have the system bled again and again, again right? SONOFA...
Click to expand...

Yes (and because this part cracks after a while anyway), and yes. You can bleed it yourself. The fill and bleed procedure is pretty simple.
http://deneau.info/ls/s6x~us~en~file=s6x33004.htm~gen~ref.htm#extract_142
 
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